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| verifiedrevid = 271214215 |
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| Watchedfields = changed |
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| ImageFileL1 =Nikkeloceen.png |
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| verifiedrevid = 386829025 |
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| ImageSizeL1 = 100px |
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| ImageNameL1 = Nickelocene |
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| ImageFileL1 = Nickelocene.svg |
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| ImageFileR1 = Nickelocene-3D-vdW.png |
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| ImageNameL1 = Nickelocene |
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| ImageFileR1 = Nickelocene-3D-vdW.png |
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| ImageSizeR1 = 140px |
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| ImageSizeR1 = 140px |
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| ImageNameR1 = Space-filling model of nickelocene |
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| ImageCaption2 = Nickelocene freshly depositied on a ] |
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| ImageFile2 = Cp2NiSublimate.jpg |
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| IUPACName = nickelocene |
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| ImageNameR1 = Space-filling model of nickelocene |
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| ImageFile2 = Nickelocen an einem Kühlfinger.jpg |
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| OtherNames = Bis(cyclopentadienyl) nickel(II) |
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| PIN = Nickelocene<ref>{{cite book |author=] |date=2014 |title=Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 |publisher=] |pages=1041 |doi=10.1039/9781849733069 |isbn=978-0-85404-182-4}}</ref> |
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| Section1 = {{Chembox Identifiers |
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| OtherNames = Bis(cyclopentadienyl) nickel(II) |
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| CASNo_Ref = {{cascite}} |
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| Section1 = {{Chembox Identifiers |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo = 1271-28-9 |
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| CASNo = 1271-28-9 |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| ChEBI = 30679 |
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| RTECS = QR6500000 |
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| UNII = JR8F745XV5 |
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| ChEBI_Ref = {{ebicite|correct|EBI}} |
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| ChEBI = 30679 |
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| RTECS = QR6500000 |
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| PubChem = 13628993 |
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| ChemSpiderID = 56178 |
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| Gmelin = 3412 |
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| EC_number = 215-039-0 |
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| UNNumber = 1325 3082 |
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| StdInChI=1S/2C5H5.Ni/c2*1-2-4-5-3-1;/h2*1-5H;/q2*-1;+2 |
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| StdInChIKey = KZPXREABEBSAQM-UHFFFAOYSA-N |
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| SMILES = C1=C(C=C1)..(C=C2)C=C2 |
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| Section2 = {{Chembox Properties |
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| Section2 = {{Chembox Properties |
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| Formula = C<sub>10</sub>H<sub>10</sub>Ni |
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| Formula = C<sub>10</sub>H<sub>10</sub>Ni |
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| MolarMass = 188.88 g/mol |
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| MolarMass = 188.88 g/mol |
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| Appearance = Green crystals |
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| Appearance = Green crystals |
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| Density = ? g/cm<sup>3</sup>, solid |
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| Density = 1.47 g/cm<sup>3</sup> |
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| Solubility = insoluble |
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| Solubility = insoluble |
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| MeltingPt = 171-173 °C |
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| MeltingPtC = 171 to 173 |
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| MeltingPt_notes = |
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| ] conditions |
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| ] conditions |
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| 60 °C at 0.1 mm Hg |
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| 60 °C at 0.1 mmHg |
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| Section3 = {{Chembox Structure |
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| Section3 = {{Chembox Structure |
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| Coordination = D<sub>5h</sub>, D<sub>5d</sub> |
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| Coordination = D<sub>5h</sub>, D<sub>5d</sub> |
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| CrystalStruct = |
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| CrystalStruct = |
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| Dipole = 0 ] |
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| Dipole = 0 ] |
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| Section7 = {{Chembox Hazards |
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| Section7 = {{Chembox Hazards |
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| ExternalMSDS = |
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| ExternalSDS = |
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| GHSPictograms = {{GHS02}}{{GHS07}}{{GHS08}} |
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| MainHazards = flammable |
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| GHSSignalWord = Danger |
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| RPhrases = 49-11-22-43 |
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| HPhrases = {{H-phrases|228|302|317|350}} |
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| SPhrases = 53-36/37/39-45 |
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| PPhrases = {{P-phrases|201|202|210|240|241|261|264|270|272|280|281|301+312|302+352|308+313|321|330|333+313|363|370+378|405|501}} |
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| MainHazards = |
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| NFPA-H = 2 |
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| NFPA-F = 4 |
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| NFPA-R = 2 |
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| LD50 = 490 mg kg<sup>−1</sup> (oral, rat) <br> 600 mg kg<sup>−1</sup> (oral, mouse) |
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| Section8 = {{Chembox Related |
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| Section8 = {{Chembox Related |
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| OtherCpds = ], ] |
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| OtherCompounds = ], ] |
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'''Nickelocene''' is the ] with the ] Ni(]-C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>. Also known as bis(cyclopentadienyl)nickel or NiCp<sub>2</sub>, this bright green ] solid is of enduring academic interest,<ref>Elschenbroich, C. ”Organometallics” (2006) Wiley-VCH: Weinheim. ISBN 978-3-29390-6</ref> although it yet has no practical applications. |
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'''Nickelocene''' is the ] with the ] ](]-C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>. Also known as bis(cyclopentadienyl)nickel or NiCp<sub>2</sub>, this bright green ] solid is of enduring academic interest,<ref>{{cite book|last=Elschenbroich |first=C. |title=Organometallics |date=2006 |publisher=Wiley-VCH |location=Weinheim |isbn=978-3-527-29390-2}}</ref> although it does not yet have any known practical applications. |
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==Structure and bonding== |
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==Structure== |
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Ni(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> belongs to a group of organometallic compounds called ]s. Metallocenes usually adopt sandwich structures in which a metal ] is sandwiched between two parallel ] rings, a structure which not only confers stability but also solubility in organic solvents and volatility (nickelocene readily sublimes under vacuum). In the solid-state, the molecule has D<sub>5h</sub> ], wherein the two rings are ]. |
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Ni(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> belongs to a group of organometallic compounds called ]s. Metallocenes usually adopt structures in which a metal ] is sandwiched between two parallel ] (Cp) rings. In the solid-state, the molecule has D<sub>5d</sub> ], wherein the two rings are ].<ref>{{cite journal|author1=P. Seiler|author2= J. D. Dunitz|title=The structure of nickelocene at room temperature and at 101 K| journal = Acta Crystallogr|year=1980|volume=B36|issue= 10|pages =2255–2260|doi =10.1107/S0567740880008539|s2cid= 93575701}}</ref> |
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The Ni center has a formal 2+ charge, and the Cp rings are usually assigned as cyclopentadienyl anions (Cp<sup>-</sup>), related to cyclopentadiene by deprotonation (this structure is similar to ]). In terms of its electronic structure, three pairs of d electrons on nickel are allocated to the three d orbitals involved in Ni - Cp bonding: d<sub>xy</sub>, d<sub>x<sup>2</sup>–y<sup>2</sup></sub>, d<sub>z<sup>2</sup></sub>. One of the two remaining d-electrons resides in each of the d<sub>yz</sub> and d<sub>xz</sub> orbitals, giving rise to the molecule's paramagnetism. With 20 ]s, nickelocene has the highest electron count of the transition metal metallocenes. ], Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>, is, however, a stronger reducing agent. |
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The Ni center has a formal +2 charge, and the Cp rings are usually assigned as ]s (Cp<sup>−</sup>), related to cyclopentadiene by deprotonation. The structure is similar to ]. In terms of its electronic structure, three pairs of d electrons on nickel are allocated to the three d orbitals involved in Ni–Cp bonding: d<sub>''xy''</sub>, d<sub>''x''<sup>2</sup>–''y''<sup>2</sup></sub>, d<sub>''z''<sup>2</sup></sub>. The two remaining d-electrons each reside in the d<sub>''yz''</sub> and d<sub>''xz''</sub> orbitals, giving rise to the molecule's paramagnetism, as manifested in the unusually high field chemical shift observed in its <sup>1</sup>H ]. With 20 ]s, nickelocene has the highest electron count of the transition metal metallocenes. ], Co(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>, with only 19 valence electrons is, however, a stronger reducing agent, illustrating the fact that electron energy, not electron count determines redox potential. |
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==Preparation== |
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==Preparation== |
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Nickelocene was first prepared by ] in 1953, shortly after the discovery of ], the first metallocene compound.<ref>{{cite journal | author=E. O. Fischer, W. Pfab | title=Zur Kristallstruktur der Di-Cyclopentadienyl-Verbindungen des zweiwertigen Eisens, Kobalts und Nickels| journal=Z. Naturforsch. B | year=1952 | volume=7 | pages=377–379 | doi=}}</ref> It has been prepared in a one-pot reaction, by deprotonating cyclopentadiene with ethylmagnesium bromide, and adding anhydrous ].<ref>{{cite journal | author = Wilkinson, G.; Pauson, P. L.; Cotton, F. A. | title = Bis-cyclopentadienyl Compounds of Nickel and Cobalt | journal = ] | year = 1954 | volume = 76 | doi = 10.1021/ja01636a080 | pages = 1970–4}}</ref> A modern synthesis entails treatment of anhydrous sources of NiCl<sub>2</sub> with ]:<ref>Girolami, G. S.; Rauchfuss, T. B. and Angelici, R. J., Synthesis and Technique in Inorganic Chemistry, University Science Books: Mill Valley, CA, 1999.ISBN 0935702482</ref> |
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Nickelocene was first prepared by ] in 1953, shortly after the discovery of ], the first metallocene compound to be discovered.<ref>{{cite journal | first1=E. O. |last1=Fischer |first2=W. |last2=Pfab | title=Zur Kristallstruktur der Di-Cyclopentadienyl-Verbindungen des zweiwertigen Eisens, Kobalts und Nickels|trans-title=On the crystal structure of biscyclopentadienyl compounds of divalent iron, cobalt and nickel| journal=Z. Naturforsch. B | year=1952 | volume=7 | pages=377–379 |doi=10.1515/znb-1952-0701 |s2cid=93978102 |doi-access=free }}</ref> It has been prepared in a one-pot reaction, by deprotonating cyclopentadiene with ethylmagnesium bromide, and adding anhydrous ].<ref>{{cite journal | last1= Wilkinson |first1=G. |last2=Pauson |first2=P. L.|last3= Cotton|first3= F. A. | title = Bis-cyclopentadienyl Compounds of Nickel and Cobalt | journal = ] | year = 1954 | volume = 76 | doi = 10.1021/ja01636a080 | pages = 1970–4 | issue = 7}}</ref> A modern synthesis entails treatment of anhydrous sources of NiCl<sub>2</sub> (such as ]) with ]:<ref>{{cite book|last1=Girolami |first1=G. S.|last2= Rauchfuss|first2= T. B. |last3=Angelici|first3= R. J.|title= Synthesis and Technique in Inorganic Chemistry|publisher= University Science Books|location= Mill Valley, CA|date= 1999|isbn=0935702482}}</ref> |
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::Cl<sub>2</sub> + 2 NaC<sub>5</sub>H<sub>5</sub> → Ni(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> + 2 NaCl + 6 NH<sub>3</sub> |
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:Cl<sub>2</sub> + 2 NaC<sub>5</sub>H<sub>5</sub> → Ni(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> + 2 NaCl + 6 NH<sub>3</sub> |
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==Properties== |
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==Chemical properties== |
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Like many organometallic compounds, Ni(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> can tolerate only brief exposure to air before noticeable decomposition. Samples are typically handled with ]s. |
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Like many organometallic compounds, Ni(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> does not tolerate extended exposure to air before noticeable decomposition.<ref>{{cite journal | first1=Anna |last1=Jaworska-Augustyniak|first2= Jan |last2=Wojtczak | title=Charge-transfer complexes of cobaltocene and nickelocene with tetrachloromethane | journal=Monatshefte für Chemie | year=1979 | volume=110 | pages=1113–1121 | doi=10.1007/BF00910959 | issue=5|s2cid=91737661 }}</ref> Samples are typically handled with ]s. |
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Most chemical reactions of nickelocene are characterized by its tendency to yield ] products with loss or modification of one Cp ring. |
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Most chemical reactions of nickelocene are characterized by its tendency to yield ] products with loss or modification of one Cp ring. |
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:Ni(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> + 4 ] → Ni(PF<sub>3</sub>)<sub>4</sub> + organic products |
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:Ni(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> + 4 ] → Ni(PF<sub>3</sub>)<sub>4</sub> + organic products |
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The reaction with secondary phosphines follows a similar pattern: |
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The reaction with secondary phosphines follows a similar pattern: |
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::2 Ni(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> + 2 ] → + 2 C<sub>5</sub>H<sub>6</sub> |
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:2 Ni(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> + 2 ] → + 2 C<sub>5</sub>H<sub>6</sub> |
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Nickelocene can be oxidized to the corresponding cation, which contains Ni(III). |
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Nickelocene can be oxidized to the corresponding cation, which contains Ni(III). |
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Gaseous Ni(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> decomposes to a Ni mirror upon contact with a hot surface, releasing the hydrocarbon ligands as gaseous coproducts. This process has been considered as a means of preparing Ni films. |
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Gaseous Ni(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> decomposes to a nickel mirror upon contact with a hot surface, releasing the hydrocarbon ligands as gaseous coproducts. This process has been considered as a means of preparing nickel films. |
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Nickelocene reacts with ] to produce ], a highly toxic organonickel compound. |
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==References== |
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==References== |
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==External links== |
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{{Nickel compounds}} |
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{{Cyclopentadienide complexes}} |
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